The invention relates to a sliding gate for metallurgical vessels, more particularly steel pouring ladles.
Sliding gates of the aforementioned kind usually comprise a housing, usually box-shaped, firmly secured to the vessel and containing two refractory plates, each having an outlet opening and movable in a straight line or in rotation relative to one another, one plate being stationary and the other movable. The two plates are secured at a pressure suitable for sealing by an externally attached frame or cover, which will be referred to herein as the frame, which can be secured to the housing. The frame has a large central recess through which an outlet jacket (or immersion tube) for the metal melt (e.g. steel) extends. The frame is made of metal, more particularly steel, and can have sliding ledges or sliding surfaces on which the movable plate can be moved to open or close the gate.
During operation, the frame is subjected to considerable mechanical and thermal stresses. The original prestress is increased, in a manner difficult to predict, by the thermal expansion at the centre of the plate which occurs during casting. The frame is internally heated by the hot parts of the gate and, more particularly, is exposed to severe heat radiation from the jet of cast metal and, possibly, reflection from the poured metal melt. These stresses, increase with the length of casting and the size of the sliding gate. The parts subject to wear have to be installed or removed very frequently, thus heating or cooling the frame or cover, which also has a disadvantageous effect.